1. Field of the Art
This invention relates to a resin composition to cope with electrostatic troubles incurred in the wrapping and packaging of semiconductors, electronic circuit substrates, electronic parts, electronics instruments, medical instruments and precision instruments, and also the anti-dust packaging of pharmaceuticals, cosmetics, foods and the packaging of dangerous materials, etc.
2. Background Art
Plastics have been used in a wide variety of fields because of their excellent properties such as transparency, durability and light weight, but since they are electrically insulating materials, various troubles due to static charges occur depending on the use or the method of use. Above all, in the field of electronics, destruction and damage to IC and LSI have become problems, and how to cope with static charges is an important and imminent topic.
For that purpose, it is necessary to improve the electrical characteristics of surrounding insulating materials that readily generate charges, and heretofore plastics kneaded with metal fibers or metal plated fibers, films and sheets blended with carbon black, graphite, tin oxide, zinc oxide, indium oxide, etc. have been made. However, these inorganic electroconductive agents cannot convert an insulating material to a material which will not be charged unless they are present to the extent that they are in mutual contact with each other in the matrix resin However, this involves drawbacks of increasing production cost and also of the physical properties possessed by the substrate material being remarkably changed Also, no transparent antistatic molded product can be made using these inorganic materials.
Alternatively an internally kneaded type antistatic agent applying a surfactant has also been widely used. This type of antistatic agent is superior to the above mentioned inorganic materials in that the amount of it to be added to a substrate material can be small, and its use does not change the physical properties of the substrate material so much and also can provide a transparent molded product with ease at low cost.
However, this antistatic agent involves some serious problems.
Thus, the effect of the antistatic agent is first exhibited when its molecules migrate to the surface of the substrate material, but the exposed agent on the surface is unstable and may be distured or removed by external conditions and factors such as temperature, humidity or contact, friction and the like. Most of the molecules of the agent present in the internal of the substrate material will migrate to the surface after the elapse of a certain period of time, and be drawn out. Accordingly, this type of antistatic agent is generally very poor in suitability and persistence of antistatic effect. Furthermore, since the antistatic mechanism itself is due to the carrier effect (ion conduction mechanism) brought about by the hydrophilic groups of the antistatic agent molecules existing on the surface of the substrate, if there occurs even a minimum disturbance in the oriented adsorption state of the antistatic agent molecules on the surface, it becomes impossible to achieve 100% decay of the charge.
Accordingly, it cannot be said in the strict sense that the aforementioned antistatic agents are a means to eliminate the influence of surrounding static charges during the transportation and use of IC and LSI-related functional products.